The present invention relates to novel compounds of the general class of perfluorinated compounds known as perfluoropolyethers and to their corresponding intermediates which are addition compounds of perfluorovinyl ethers and fluorinated monohydric alcohols.
Perfluoropolyethers possess excellent chemical and thermal stability which ensures a wide field of application for these compounds. They are useful as heat transfer media, sealing liquids, lubricants under extreme chemical conditions, additives for oils and greases, turbine propellents and hydraulic liquids. They exhibit low dielectric constants, high breakdown voltages and low loss factors in alternating fields, which makes them particularly suited for applications in the electrical area. In the electronics industry, for example, perfluoropolyethers are particularly useful as vapor phase soldering fluids. They also find applications as convection cooling liquids in transformers or similar devices. Their excellent dissolving power for oxygen and carbon dioxide enables them to be used as oxygen conveyers in heart-lung machines and also directly as blood substitutes in living organisms. These products also find applications in many spheres of nuclear and chemical engineering. Because of their outstanding chemical resistance they are superior to the propylene oxide fluids that hitherto dominated these application fields, especially at temperatures above 200.degree. C.
Currently available vapor phase soldering fluids can be relatively expensive to manufacture, or they may release toxic vapors at the temperatures at which they are used. In addition, some have a high solubility in soldering rosin which requires expensive reclamation and reduces fluid life.
Compositions which most closely resemble the compositions of this invention can be found in U.S. Pat. No. 3,962,348 and its British counterpart, GB No. 1 450 467. These two patents describe polyfluoroethyl and polyfluoropropyl ethers having the following formula: EQU [C.sub.x F.sub.2x+1 OCF.sub.2 ].sub.a Rf[OC.sub.x F.sub.2x+1 ].sub.b
where
Rf=C.sub.n F.sub.2n+2 -(a+b); PA1 n=1-10; PA1 a,b=0-4; PA1 x=2 or 3. PA1 b=0-2, with the proviso that when b=O,R.dbd.CF.sub.3, and when b=1 or 2,R.dbd.F; PA1 c=0-8; and PA1 d=5-18. PA1 b=0-2, with the proviso that when b=0, R=CF.sub.3, and when b=1 or 2, R=F; and PA1 c=0-8. PA1 X=H or F; PA1 d=4-16; and PA1 e=1-2. PA1 b=0-2, with the proviso that when b=O, R=CF.sub.3, and when b=1-2, R=F; PA1 c=0-8; PA1 d=4-16; PA1 e=1-2; and PA1 x=H or F. PA1 (a) maintaining the initial fluorine concentration in the inert gas stream until from 1 to and including 5% of the theoretical amount of fluorine has been introduced into the reaction solution; PA1 (b) increasing the fluorine concentration to a value up to and including 33% by volume and maintaining that concentration until up to and including 12% of the theoretical amount of fluorine has been introduced into the reaction solution; PA1 (c) increasing the fluorine concentration to a value up to and including 50% by volume and maintaining that concentration until up to and including 120% of the theoretical amount of fluorine has been introduced into the reaction solution; and PA1 (d) increasing the fluorine concentration to the desired realistic maximum value and maintaining that concentration until up to and including 200% of the theoretical amount of fluorine has been added to the reaction solution.
with a+b greater or equal to 1; and
Perfluoropentaerythritol tetraethyl ether and perfluoropentaerythritol tetrapropyl ether are examples of such compounds. Both patents describe the synthesis of aliphatic and cyclic perfluoroalkyl ethers in high yields in which tetrafluoroethylene or hexafluoropropylene adducts of aliphatic or cyclic alcohols are subjected to electrofluorination.
The reaction of a perfluorovinyl ether and a monohydric alcohol is described by A. V. Tumanova et al., in Zhurnal Obshchei Khimii, Vol. 35, No. 2,399 (1965). The addition compound formed by methanol and perfluoromethyl vinyl ether, which is described therein, differs from the intermediate products of the present invention by virtue of the fact that the alcohol used is not fluorinated. Furthermore, no subsequent fluorination step to produce a perfluoropolyether is described. No prior art is known which describes addition compounds made from the perfluorovinyl ethers and fluorinated monohydric alcohols which are used in the present invention.